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Molecules, Biodiversity, Food and Health

Biological Molecules
(a) describe how hydrogen bonding occurs between water molecules, and relate this, and other properties of
water, to the roles of water in living organisms
Water is a polar molecule. This is because the oxygen atom pulls the shared electrons towards it,

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(c) describe, with the aid of diagrams, the formation and breakage of peptide bonds in the synthesis and
hydrolysis of dipeptides and polypeptides
A covalent peptide bond forms between the H of the amine group of one amino acid and the
OH from the carboxyl group of another. This…

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(i) compare the structure and function of haemoglobin (as an example of a globular protein) and collagen (as
an example of a fibrous protein)

4 polypeptides subunits
2 alpha chains and 2 beta chains
1 haem group per polypeptide
4 haems per molecule
prosthetic group is haem which contains Fe2+…

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Made up of glucose joined by 1,4 bonds in a chain no branches.
Alternate glucose subunits are inverted
Forms straight chains which form fibres with hydrogen bonding between chains
The glycosidic bond can only be broken down by a cellulose enzyme, which herbivores
have, but humans do not
Forms plant…

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Phosphate may have carbohydrate attached forming glycolipids involved in cell signalling
Small, thin molecules that can fit into the lipid bilayer giving strength and stability
Used to form steroid hormones

(r) describe how to carry out chemical tests to identify the presence of the following molecules:
protein (biuret test),…

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Nucleic acids

(a) state that deoxyribonucleic acid (DNA) is a polynucleotide, usually double stranded, made up of
nucleotides containing a nitrogenous base (adenine(A), thymine(T), cytosine(C) or guanine(G)), the sugar
deoxyribose and a phosphate group

(b) state that ribonucleic acid (RNA) is a polynucleotide, usually single stranded, made up of nucleotides…

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The mRNA attaches to a ribosome
Then tRNA molecules bring amino acids to the ribosome in the correct order, according to the base
sequence on the mRNA
The amino acids are joined together by peptide bonds to give a protein with a specific tertiary

If there is a mutation…

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If the pH change affects the charge on the amino acids at the active site, then the properties of
the active site change and the substrate can no longer bind
At high pH values, the ­COOH group will dissociate to become a charged ­COO group
Up to a certain…

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As before, but keeping the temperature and the number of potato discs the same and
changing the concentration of hydrogen peroxide in each test tube

(f) explain the effects of competitive and noncompetitive inhibitors on the rate of enzymecontrolled reactions,
with reference to both reversible and nonreversible inhibitors
Competitive inhibitor…

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Food & Health
Diet & Food Production

(a) define the term balanced diet
A diet that contains all the nutrients of the nutrients requires for health and growth in the correct

(b) explain how consumption of an unbalanced diet can lead to malnutrition, with reference to obesity
Malnutrition is…


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